Angle encoding apparatus



Oct. 6, 1964 R. c. WEBB 3,152,324

ANGLE ENCODING APPARATUS Filed March 4, 1959 '7 Sheets-Sheet 1 no INVENTOR. RICHARD c; WEBB BYI v Oct. 6, 1964 R. c. WEBB 3,152,324

ANGLE ENCODING APPARATUS Filed March 4, 1959 7 Sheets-Sheet 2 IN VVVVV RI RICHARD C. WEBB BYI 4 War 7) Oct. 6,

ANGLE! ENCODING APPARATUS Filed March 4, 1959 7 Sheets-Sheet 3 Transducer Phase Phase Detector Detector ei 63 T75 /97 73 69 L 4 I 96 90 9| 65 Fr e qu ency Jitter \IOOO -67 Jitter Compensator Compensator /95 Controlled Controlled Oscillator Oscillator 99 98 7 (Reference) (Variable) u 7 8' t Phase Comparator and Up-Down Separator l 83\ Zero Crossing 1 Up Down Coincidence Detector Continuous 86 Reversible Output Counter Vernier l I l l W- J J J J J J 93 Degree Vernier FIG. 3

lNVENTORI RICHARD C. WEBB Oct. 6, 1964 R. C. WEBB Filed March 4, 1959 '7 Sheets-Sheet 4 Variable Reference Frequency Frequency Input Input I06 los III) |O| Adder Integrator Adder /|o3 I09 ||2\ MN] m us Amplitude Amplitude Detector Detector x ll 'FfY Schmitt Schmitt Trigger Trigger Fill 'U'L Differen- FU'I tiator t20-- w Differen- |3o tiator Inverter HAND" "AND" Gate I I Gate 'T' 85/ T "Add" "Subtract" Output FIGA Output INVENTORI RICHARD C. WEBB Oct. 6, 1964 R. c. WEBB ANGLE ENCODING APPARATUS '7 Sheets-Sheet 5 Filed March 4, 1959 Owm bvm

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INVENTORI BYI RICHARD 0. W588 frz ra y '7 Sheets-Sheet 6 R. C. WEBB |NVENTOR= RICHARD C. WEBB Y= lrrar rsy,

ANGLE ENCODING APPARATUS Oct. 6, 1964 Filed March 4.

Oct. 6, 1964 c, WEBB 3,152,324

ANGLE ENCODING APPARATUS Filed March 4, 1959 7 Sheets-Sheet '7 FIGURE 7 United States Patent 3,152,324 ANGLE ENCODING APPARATUS Richard C. Webb, Brownfield Heights, Colo, assignor, by mesne assignments, to hell 8; Gossett Company,

Morton Grove, llll., a corporation of Illinois Filed Mar. 4, 1959, Ser. No. 797,264 11 Claims. (Cl. Mil-34?) This invention relates to apparatus and circuitry for providing continuous measurement and digital encoding of the relative phase difference between two substantially sinusoidal electrical signals of equal frequency but variable phase angle.

In its preferred form the invention finds a principal application in the digital encoding of the relative phase difference between two electrical signal waves generated under the control of a precision electrostatic shaft-position-transducer which may be, illustratively, of the form described by this applicant in United States patent application, Serial No. 578,853, filed April 17, 1956, now US. Patent No. 2,930,033. The transducer in its preferred form is a generator of two sinusoidal electrical signals of known and selected frequency, normally identical and one of which is of reference phase while the other adjusts to an advanced or retarded phase position in proportion to angular movements imparted to the mechanical shaft. Some phase measuring devices of the above type are designed to produce an electrical phase shift of precisely 360 electrical degrees for each mechanical degree of mechanical movement. By this invention a continuous electronic phase angle encoder is used in conjunction with an angle transducer to provide an apparatus by which angular positions of a shaft are interpreted in terms of digital signals with an accuracy considerably greater than that achieved by methods heretofore known or suggested.

The techniques embodied in this invention avoid the need for sampling of the analog information to be encoded into digital form, as is common in many analogto-digital encoding schemes, so that the digital information is continuously available from the electronic apparatus and there is no delay entailed in the acquisition of information, as has been inherent in encoders of earlier designs.

According to the principles of this invention a large number of applications for shaft encoding apparatus of high precision manifest themselves. Such applications, by way of example, may be in the continuous measurement of azimuth and elevation shafts in optical tracking instruments and radars employed in guided missile range instrumentation; the measurement of angular displacements of stable platforms; the registration of angular settings of rotary tables used in machine tool applications, as well as many other applications that will suggest themselves to those skilled in the art to which the invention is directed.

The broad principle involved in the electrical phase angle measuring disclosed by the invention herein to be set forth is that of first relating each of the two signals whose relative phase is to be measured to selected harmonics of sufficiently high order to permit the harmonic frequencies to be used as a time measuring scale of fractional portions of the basic or fundamental signals.

In accordance with the invention, and that preferred form of it herein to be particularly discussed, the one thousandth harmonic of a given wave is used as a scale, which permits making measurements to a least count or granularity of A of a wavelength or 0.360 electrical degree. As the invention will herein be described, each of the two basic signals is related to a selected harmonic of the same order (the one thousandth harmonic, for example) and these harmonic signals are applied to a summing circuit wherein they are permitted to, interfere constructively and destructively (additively and subtractive- 1y) with one another in accordance with movements or shifts in the relative phase position of the basic signals. in a case where the related signals are chosen as the onethousandth harmonics, one thousand interference maxima and minima will occur as the basic electric waveforms are shifted in phase by one wavelength. If this amount of electrical shift is produced by a shaft position transducer due to rotation through one mechanical degree, then a summation of interference maxima is a measure to one thousandth part of a mechanical degree or increments of 3.6 sec. of arc.

in the event the mechanical shaft is rotated first in one direction and then in the other, that is, for instance, clockwise and counter-clockwise, it becomes necessary to register the number of up counts (as for an increasing phase change) as Well as the number down counts (as, for instance, for a decreasing phase change) to maintain the latest information concerning the shaft setting. One part of this invention relates to an up-down separator which functions in conjunction with the interference detector to transmit a series of up counts over a signal channel to a digital counter, as well as a series of down counts over another signal channel to the same counter, the counter being one of a type adapted to be advanced by up counts and retarded by down counts, thereby retaining at all times a net count at any given instant.

Mechanical transducers of the foregoing type, even when made to the ultimate limit of mechanical perfection, inherently introduce amplitude and phase perturbations in the two basic signals derived therefrom. These mechanical imperfections result in a so-called jitter in the produced results unless compensated but by this invention they are minimized and substantially compensated for by purely electrical means according to the circuitry herein to be described. The mechanical transducers simultaneously produce both the amplitude and phase components of the mechanical perturbation. Fortunately, only the phase errors register in the electronic encoding apparatus which is substantially insensitive to amplitude disturbances. Accordingly, it becomes possible to amplitude demodulate the perturbation wave to produce a signal voltage that is substantially a replica of the disturbance. This invention provides for recovering such a voltage which is then introduced into an appropriate elec trical phase-locking circuit to be used to tie the high frequency harmonic to its base signal in such a manner as to introduce a counter-perturbation into the phase-locking circuit in such a way as to oppose the natural perturbation coming directly from the phase modulation of the base signal. The combined effect is a neutralization of the disturbance.

With the foregoing in mind it becomes apparent that one of the many objects of the invention is that of pro: viding for substantially continuously exhibiting and recording as measured value of great detail indications of certain electrical phenomena not otherwise readily comparable.

A further object of the invention is that of providing indicating apparatus which furnishes a continuous decimal display of measured angles in degrees and minute fractional parts thereof in an angle measuring assembly.

A further object of the invention is that of providing two electrical factors of substantially like frequency but variable phase, Where the phase displacement is made substantially instantaneously available, so that measurement provided by an electronic system serves to quantize and encode the phase angle produced between the two generated or provided electrical waves and to present their form as a decimal fraction of a detail represented P atented Oct. 6, 1964 by an arcuate displacement of the order of 3 seconds of arc.

Other objects of the invention are to provide electronic Vernier measurements of phase angle differences between two produced electrical waves where the comparison is substantially insensitive to amplitude variations in the generated and compared waves.

A further object of the invention is that of providing indications of immediate availability of whether or not the phase relationship between a reference or standard wave and one to be measured is lagging or leading with respect to the other, or whether or not there is precise coincidence between the two conditions.

Still another object is that of electrically compensating for inherently present amplitude and phase pertubations of a pair of electrical waves generated by electromechanical transducers.

Other and further objects of the invention are those of providing an angle and encoding system or device of high precision, which is generally self-calibrating, extremely light in weight, requiring minimum service, as well as space requirement and from which a readout accuracy of at least one part in almost one-half million is realizable.

Other and further objects of the invention are those of providing a variety of readout alternatives in an angle and encoding system where both decimal and binary decimal representations may be had and where, in the production of the representations, automatic resets can be had.

Other and further objects of the invention will, of course, be recognized as those of obtaining a high degree of accuracy, a high degree of insulation, a continuity of readout time, a general insensitiveness to temperature changes, a lightness of weight, a high efiiciency and general freedom from complex circuitry in apparatus and circuitry of the foregoing type so that the marketing price can be at a minimum.

Other and further objects and advantages of the invention will become apparent and at once suggest themselves to those skilled in the art to which the invention is directed in the following description as considered particularly in connection with the accompanying drawings wherein;

FIG. 1 is a schematic diagrammatic view depicting in elementary form a form of electrostatic tone generating apparatus providing one form of arrangement in electromechanical transducer to develop each of a standard or reference frequency and a variable phase frequency for comparison with the standard;

FIG. 2 is an isometric view of the electromechanical transducer to indicate one mechanism to introduce phase shifts between two developed electrical waves;

FIG. 3 is a diagrammatic view presented to show in block diagram form the component parts comprising a preferred form of the apparatus herein to be described;

FIG. 4 is a block diagram of the up-down separator shown as one part of the diagrammatic view of FIG. 3;

FIG. 5 is an illustration of one form of circuit for use with the components depicted by FIG. 3 and illustrating in particular one form of zero crossing coincidence detector;

FIG. 6 is a circuit diagram of the up-down rator of FIG. 4; and

FIG. 7 is a circuit diagram of a jitter compensating circuit for compensating for amplitude changes in the generated wave forms provided by the rotor and stator combinations as depicted, particularly, by FIG. 2.

For the purpose of illustrating the present invention in one of its aspects it will be assumed, for instance, that an eletcro-mechanical transducer provides the wave generating mechanism. This transducer has a driven shaft element 11 which is turned continuously and uniformly at constant speed by means of a suitable driving motor (not shown but connected in any desired way to sepa- Ail drive the shaft 11). The motor is supplied with input motive power from any desired source (not shown) connected to it in well known fashion. Carried upon the shaft 11 are a plurality of rotor elements 15 provided at their outer peripheral edge with teeth elements 17 which are separated from each other by slots or recesses 19. The teeth are formed usually by engraving the slots or recesses on the periphery of the surface of the rotor so that the unengraved portions represent the teeth. Illustratively, the rotor periphery may have uniformly spaced thereabout 360 teeth separated by a like number of slots. Each tooth is thus spaced from each adjacent tooth by one degree intervals on centers. Thus, for simplicity of reference and explanation of workings of one form of this apparatus, reference may be made to what may be regarded as a 360 degree device.

The stator elements 26 and 20 each have a similar number of teeth 21 and likewise a similar number of recesses or slots 23, separating these teeth. The inner diameter of the circular component formed by the stator 2th or 20' is made just slightly larger than the outer diameter of the rotor element and the teeth 17 so that with the rotor positioned to turn within the stator a very small air gap exists between the teeth 17 and 21 when these are brought as close to each other as possible.

The rotor element 15 is connected to ground or to a source of fixed potential 25 by way of the indicated conductor 27 and the brush or slip-ring on the shaft 11. Electrical connection is made to the stator 26 through the conductor 28 which connects to ground 25 through the charging resistor 29 and the source 31. The stator element is thus maintained insulated from ground 25 and, with rotation of the stator element, the varying capacitance between it and the rotor element 15 is supplied with charging current from the source 31 through the resistor 29. The rotation of the rotor element causes the teeth of the stator successively to be aligned with the rotor teeth and to be separated from the rotor teeth producing charging of the condenser which is potential to the capacity between the rotor and the stator. This variation in capacitance then induces a corresponding change of the charging current from the source and produces across the resistor 2a a voltage which becomes available on the conductor 53 which may have the form of that wave indicated immediately beneath the conductor. A like frequency wave is generated by the rotorstator combination 19, 20' with the output wave available on conductor 55. Primed numbers in FIG. 2 represent components like those described in producing the waveform available on conductor 53.

When the rotor element is provided with two sets of teeth, as in FIG. 2, both are carried upon the shaft 11 and each is positioned adjacent to the other, and each is adapted to rotate relative to its own related stator element so that it becomes apparent that two separate 5.4 kc. per second waves are developed and available on conductors 53 and 55.

In applying the invention to apparatus for encoding interference effects which constitute a measure of angular departures of one element relative to another the driven elements, such as the rotors 15 are caused to turn relative to a pair of stator elements 20 and 20'. One of the stator elements, such as element 20, remains in fixed position at all times and the other is adjustable. The other of the stator elements, such as 2t), is subject to being changed in its angular position relative to the rotor with the changes resulting from induced mechanical turnings of a controllable component such as the conventionally represented control shaft 22 (FIG. 2). In each instance the rotor elements revolving internally of the stator elements 2@ and 2t), produce output electrical waves of substantially sinusoidal form Whose frequency is substantially identical, although the phase of the generated waves produced by the rotor-stator combination which is adjustable is subject to change relative to the reference frequency from the other wave-generating component. In this sense the phase may advance or retard relative to the reference.

In practicing the invention the element Whose angular state is to be determined is rotated (as indicated by the arrow in FIG. 2) and turns the shaft 22 and with it the hub 24 and stator 2%. This introduces a phase change in the waveform available on conductor 55 as compared to that available on conductor 53. This change is then precisely determined.

By FIG. 3 of the drawings the transducer element to produce the reference and variable phase electrical waves is shown conventionally at 51. It will be noted that for the purpose of indicating the fact that the variable phase generated wave may either be retarded or advanced with respect to the reference that the rotary transducer is shown as capable of revolving in either a clockwise or counter-clockwise direction, as designated by the arrows adjacent to the shaft 22 in each of FIGS. 2 and 3. Output voltages of a waveform substantially like those forms shown adjacent to the transducer are provided on the conductors 53 and 55, the waveforms on the conductor 53 for reference purposes being considered as developed from the combination of the permanently fixed stator 20 and its rotor with teeth 17 and those waveforms developed on the conductor 55 being considered to have been developed by the relative change between rotor 15 and its teeth 17 relative to the stator element 2d, the relationships, of which are adjustable with respect to each other, as already explained. The frequency of the output voltages on conductors 53 and 55 may be chosen at any value desired, although it will be understood that the chosen generated frequency is determined by the number of separate pole pieces on the rotor and stator elements and the speed of rotation of the elements. For instance, if each rotor and stator is provided with 360 teeth and the rotor is turned in the shaft 11 relative to the stator at a speed of 900 r.p.1n. the output frequency on conductors 53 and 55 will be a waveform repeating at a frequency of 5.4 kc. Concurrently with the generation of the reference and variable phase voltages at the assumed frequency, which is here given solely by way of example to provide an illustration of one form of the operation of the apparatus and circuitry herein to be set forth, there is generated in the conventionally indicated generators 57 and 59 for the reference and variable frequency panels respectively oscillations which occur at a harmonic of the frequency developed from the transducer.

The oscillators 57 and 59 are not shown by circuit components since these are of any form Well known in the art. One form of the oscillator which has proved quite satisfactory is the well-known Colpitts-type which provides extremely stable operation. The generated frequency is, however, subject to control, as desired, in wellknown fashion. The reference and variable phase output voltages are developed and available along the conductors 53 and 55 from which they are supplied to suitable phase detectors 61 and 63, the character of which is well known and need not be described herein in detail. Suffice it to say that the phase comparison of voltages is made between a subharmonic of the reference and variable master oscillator frequency as supplied to the phase detectors from frequency dividers 65 and 67 through conductors 69 and 71.

The frequency dividers 65 and 67 are of any well-known type suitable for providing a frequency division. In the illustrated case a frequency division of one thousand has proved satisfactory so that in the phase detectors 61 and 63 a phase comparison is made between the master control oscillator at its one-thousandths subharmonic and the developed generated frequency. The technique followed in this phase detector is essentially similar to that adopted in the well-known form of television circuitry wherein the so-called fly wheel type of synchronization is established.

any phase differences between the frequency of the waveform applied via the conductors 69 and 53 to the phase detector 61 or via the conductors 71 and 55 to the phase detector 63 will then manifest themselves as a suitable control voltage available respectively on the conductors '73 and 75 which then may be supplied as a DC. control voltage, for instance, which is fed back to control and adjust the frequency of the oscillators 57 and 59, respectively. This control may be provided in well-known manner, such as by applying the phase-detected voltage as a gain control signal for the usual form of reactance tube whose output controls the magnitude of either an inductive or capacitive component in the oscillatory circuit of the oscillators 57 or 59, depending upon which form of signal channel is to be selected. In this way an automatic frequency control loop is established between the oscillators 57 and 59 and the voltages developed on the conductors 53 and 55 through the action of the phase detectors 61 and 63, as the case may be.

Output voltages from the oscillators 57 and 59 comprising the master and variable control voltages occurring at a harmonic frequency of that developed by the transducer are also supplied by way of conductors 77 and 79 to a phase comparator and so-called up-down separator 81, which has been shown in block form on the schematic diagram of FIG. 3 but which circuitry is further outlined and described in substantial detail in the showing of FIG. 6 and will be further referred to in connection with the description of such figures. Sufiice it for the moment, however, to state that in the phase comparator and up-down separator 81 output signal voltages of general pulse characteritsics are provided and appear on the output conductors 83 and 555 as pulses to be added or subtracted in a reversible counter mechanism. The counters are shown conventionally by the counter components 86 and 87 which each comprise a plurality of separate indicator tubes and of which respectively and for illustrative purposes may be considered as representing degrees of phase shift by the counter 86 and tens, hundreds and thousands of degrees by the counter, schematically represented at 87 and thus forming a so-called Vernier counter. The counter itself is in the form of a tube which has become known in the art as a Burroughs-type and illustratively may be of that form known as the BD301. Each output pulse available on the conductors 83 or 35 and indicative of either an add or subtract pulse is, accordingly, effective to move the counted indication on the counter Vernier up or down one step and thus register increasing or decreasing angle, and, of course, a phase change which is either increasing or decreasing. To illustrate, and still assuming the specific values here depicted, it will be appreciated that if the reference phase oscillator 57 operates at a normal 5.4- me. and the variable phase oscillator 59 responds to changes in the variable phase input signal to maintain one thousand cycles for every transducer cycle, if the transducer input 55 is turned one mechanical degree thus changing the relative position of one stator tooth relative to a rotor tooth, the variable phase oscillator 59 will generate one thousand cycles more than the reference phase oscillator 57. Likewise, if the angular relationship is changed one mechanical degree clockwise the variable phase oscillator 59 will generate one thousand cycles less than the reference oscillator 57. By the same token, if the input to the transducer is rotated at constant velocity of one degree per second in a clockwise direction, for instance, the output of the variable phase from the transducer will be 5.401 kc. and the variable phase oscillator 59 will then be forced by the controlled voltage to operate at 5.401 me. which is 1000 cycles per second faster than the reference phase oscillator. Since the signals from both the reference phase oscillator 57 and the variable phase oscillator 59 are applied by way of conductors 77 and 79 to the phase comparator and up-down separator, it will be appreciated that as the variable phase oscillator output moves one cycle with respect to the reference phase oscillator, the

phase comparator goes through one null and one reenforcement. In case the variable phase oscillator tends to operate faster than the reference oscillator there is produced in the output of the phase comparator and up-down separator 31 on the conductor 83 an up count for each passing cycle. It follows that if the variable phase oscillator tends to operate slower than the reference oscillator a down count or a pulse is produced on the conductor 85 for each passing cycle. If there is a frequency change which is common to both phases no so-called up and down counts are produced. Consequently, the effects of small power line frequency changes or hunting conditions to the drive motor are cancelled.

It is desirable to reset the Vernier counter 87 to a Zero state whenever absolute coincidence is achieved between the variable and reference phase signals at the assumed l000:1 frequency dividers 65 and 67. The resetting is achieved under the control of the zero crossing coincidence detector conventionally shown at 89 in FIG. 3 and more particularly set out in circuit form in FIG. 5 with the signals serving to control the zero crossing coincident detector 89 being fed by way of the input conductors 99 and 91, these representing, illustratively, an input determined by the reference and variable phase osciliators 57 and 59 reduced in frequency by an order of I000. The input signal supplied by way of the conductors is generally in pulse form and serves to provide a zero position indication once each cycle. The output signals from the zero crossing coincidence detectors 89 which control the Vernier counter 87 then appear on the conductor 93.

The continuous output counter section 86 is controlled by means of a code plate assembly (not shown), operated in conjunction with the transducer. The code plate assembly is known in the art and provides a control which is indicative of a continuous output of the correct degree information. Control is effected through a brush selecting gate (not shown) which is controlled from the hundreds decade of the up-down counter which determines the selection of a leading or lagging brush in the code plate system. For instance, as is known in the art, for a digit of through 4 in the hundreds counter a leading brush is energized and for a digit 5 through 9 a lagging brush is energized. The code plates then produce a binary coded decimal form of continuous output of the correct degree information and there is no ambiguity in the degree crossovers because the Vernier counter 87 is continuously selecting the correct brush to go with the prevailing Vernier indicator or reading. This form of control of the output is known and, is therefore, not specifically diagrammed by FIG. 3.

Because of minor mechanical imperfections which are inherently present in mechanically driven devices, despite their manufacture to the limit of mechanical perfection, disturbances which will herein be termed jitter frequently arise, while various causes may bring these effects about, one cause often is that due to the rotor shaft running very slightly eccentric so that the amplitude of the generated output voltage waves at the reference and variable frequencies, as appears on the conductors 53 and 55, may vary very slightly. The variation can be in either or both amplitude and phase and even where this is an extremely low frequency change occurring over a long period of time it is sufiicient to cause certain imperfections in the operation unless compensation is provided. It is impossible in general to provide mechanical compensation where the precision of manufacture of the transducer component is the greatest obtainable. Accordingly, this invention makes provision for introducing with the signal generating circuitry an electrical compensator to avoid the detrimental effects of mechanical power jitter.

One form of circuitry to provide for compensating for such pertubations has been schematically represented in FIG. 3 as the block diagram form of jitter corrector conventionally shown at @4 and 95. Input signals to the jitter correctors 94 and 95 are provided by way of conductors 96 and 97. Produced correction signals from the compensators 94 and 95 are then supplied by way of conductors 93 and 99, respectively, to the input of the oscillators 57 and 59. The jitter corrector is further shown and discussed in connection with FIG. 7 of the drawings to which more specific reference will be made at a later point in this description. Suffice it to state at this point that signal voltage is developed which is provided for the purpose of initiating a very minor phase modulation of the oscillator 57 or 59, as the case may be, in order to compensate the phase error in the control of the oscillator.

Reference may now be had to the block diagram form of the phase comparator and up-down separator 81 which is in dia rammatic form in FIG. 4. The voltages available upon the conductors 77 and 79, representing, respectively, the assumed 5.4 mc. reference frequency and variable frequency input are shown as each being supplied to adder circuits 1% and 1193 by way of conductors and 1% to the adder circuit 111 and by way of conductor 107 integrator 17% and conductor 111 to the adder 113. The integrator 16%? through which the reference frequency signal is applied serves to provide a 90 phase lag of the frequency input to the adder 1% with respect to the phase at which this reference frequency is supplied to the adder 191. The adder components, as well as all other components diagrammatically shown by FIG. 4 will be referenced by one preferred form of circuit as shown by FIG. 6. Sufiice it for the moment to point out that the adder circuits 1 1 and 1G3, respectively, are the well-known resistance combination circuit elements which serve to combine and add the two inputs provided.

The waveforms shown adjacent to the output conductors 112 and 113 from the adders 161 and 103, respectively, represent the beat frequency occurring between variable and reference phase inputs where it is assumed that the variable frequency is increasing very slightly with respect to the reference frequency input and illustrate a condition where a 1 kc. beat is provided for a change in the angular position of the rotary shaft element of 1 per second. In the illustrated curves immediately adjacent to the conductors 112 and 113 it can be seen that the beat frequency waves are shown 90 out-ofphase with each other. While the beat frequency has been represented, illustratively, by the waves adjacent to the curves 112 and 113 occurring at a frequency of l kc. it can be appreciated that if the relative change occurs at a rate of less than 1 per second the period of the beat frequency wave will be considerably longer and, of course, the closer that no angular change results the closer the curves will approach a D.C. or steady state condition.

The added voltages on the conductors 112 and 113 are then supplied to the amplitude or peak detectors 114 and 115, respectively, which are depicted more particularly by FIG. 6. Any form of detector which measures the peaks of the voltages resulting is suitable for the control and the waveforms adjacent to the output conductors 116 and 117 represent, illustratively, the rectified wave supplied to the input of detectors 114. and 115. This amplitude varying wave is then supplied to any suitable form of trigger circuit or flip-flop of which the well-known form of Schrnitt trigger circuit, as conventionally shown at 118 and 119 is suitable. Again, these trigger circuits are well-known but are, nonetheless, diagrammatically shown in one of their preferred circuit forms in the description and diagram of FIG. 6.

The Schmitt triggers 118 and 119 may conventionally be set to trigger on and off in accordance with the conditions depicted by the dotted lines passing through the waves of the curves positioned adjacent to conductors 116 and 117. The triggering is such that at the output of each Schmitt trigger 118 and 119 an on-off wave of pulsed formation appears with the wave on the conductor 121 being 90 phase-delayed relative to the wave on conductor 129. These output pulses then provide a trigger control means for developing the signal voltages of the 9 add and subtract output pulses appearing on the conductors 83 and $5, respectively, as diagrammed by FIG. 3.

The signal outputs from the Schmitt triggers are supplied to so-called and gates 122 and 123, respectively, with the pulses appearing on the conductor 120 (see waveform generally adjacent to conductor 120 for illustrative form) being applied to the gate 122 by way of conductor 12-1 and to gate 123 by way of conductor 125. These waves constitute conditioning pulses for permitting under a suitable control action of the output from Schmitt trigger 119 an operation of either gate. The output from the Schmitt trigger 119 is differentiated in signal dilferentiators 12d and 127 with the output from the differentiator 127 being applied by way of conductor 129 as the supplemental voltage effecting an opening and closing of the gate 123. The differentiated voltage output from the ditferentiator 25 is applied by conductor 1311 to a signal inverter 131 whose output is supplied by way of conductor 132 to the and gate 122.

Accordingly, it can be appreciated that the output from the trigger 119 actually serves as a supplemental control on the gates 122 and 123 and that the control effected thereby is such that a differentiated pulse effective to add with a continuation pulse on the and gate 123 is ineffective on the and gate 122. Likewise, since the polarity of the pulse which controls the and gate 122, is op posite to that of the pulse supplied to the and" gate 123, the control is precisely opposite. Thus, for instance, if it be assumed that inputs to the gate 123 are as represented by the waveforms adjacent to conductors 12d and 129, respectively, it can be seen that the positive differentiated pulses will cause an opening of gate 123 and a control voltage of the form shown adjacent to the conductor 85 will appear at a time coinciding with each positive portion of the differentiated pulse adjacent to the conductor 129. Similarly, with the control of the gate 122 being effected by a differentiated pulse which is of opposite polarity to that shown adjacent the conductor 129 and which is of a polarity such as that shown by a wave adjacent to the conductor 1211 it can be seen that the gate 122 will open on each positive portion of the differentiated wave. In this way the positive sections of the Schmitt trigger output provide conditioning for enabling pulses effective at the gates 123 and 122 and the gates are triggered in accordance with the presence or absence at the time of a positive differentiated pulse. The circuit diagram of FIG. 6 has described this part in detail.

Referring now to FIG. 6, a form of circuit is illustrated which depicts one preferred form for providing the up down separator as controlled by the generated high frequency reference and variable sources, as in the diagrammatic showing of FIG. 4. The reference voltages are supplied on the conductor 77 and the variable input is supplied on the conductor 79 to a first portion of the channel which includes the adder 1M, the detector 114 and the trigger circuit 113 to supply the and gate 122. The refcrence signal is available on the conductor '77 and applied to the input or grid electrode of a tube 135 having its plate voltage supplied from a source of positive voltage (not shown) poled with its positive terminal connected to the terminal point 136 and its negative terminal connected for instance to ground 137. Plate voltage for the tube 135 is applied through the resistor 138. The input signal voltage at the reference frequency is supplied on the tube grid, the grid being biased by the grid resistor 139. Signal output voltages are available (the tube output being connected as a cathode follower) across the cathode resistor 140 and then supplied through the condenser 16-1 and resistor 142 across an adding resistor 143.

The tapping point for connecting the output to the cathode resistor ltd ti provides for effecting a balance of the signal amplitude of the reference phase with respect to that of the variable phase and, accordingly, is adjustable as indicated by the tapping point. With the input signal of the reference phase being supplied as stated the variable phase signal is then supplied to the terminal point connected to the conductor '79 and through the conductor 145 to the tube 146. Tube 146 is supplied with operating plate potential through the plate resistor 147 from the source connected at the terminal point 145. The input signal of the variable phase is applied to the input or control electrode of the tube 146 having its grid resistor 149 connected as indicated and providing bias. The tube cathode is loaded by the cathode resistor 151 connecting at its lower end to ground 137. Tube 146, like the tube 135, is also connected as a cathode follower. To balance the amplitude of the output voltage due to the variable phase input, the tapping point on the cathode resistor 151 may be adjusted up and down to provide a voltage divider,

Output signals are then fed through the capacitor 153 and the resistor 154 so that across resistor 143 the two signals, that is, the output signal from the tube 135 (the reference signal) and the output from the tube 146 (the variable signal) are combined and become available on the output conductor 155. This output is an amplitude varying envelope which contains the 5.4- mc. carrier assumed. Other circuit components connected with the tubes 135 and 146 are believed to be too wellknown to require further discussion, it being, of course, apparent that the input signals may be fed into the input of the tubes through coaxial cables, as indicated, and that high frequencies may be bypassed from the tube outputs by the indicated capacitors.

In most instances the output representing the addition of the voltages applied to the tubes 135 and 146 is then supplied to an amplifier tube 157 via the output lead 155 connected to the inner grid or control electrode element. The tube 157 is preferably of the pentode variety. The tube screen electrode is maintained at a positive voltage from the terminal point 136 via the resistor 158 with the capacitor 159 connecting it to ground potential. The tube plate is supplied with positive potential relative to the tube cathode through the usual plate resistors 16d and 161 with RF bypass provided by the condenser 162. The plate potential is also supplied through a pair of serially connected inductors 163 and 164 (preferably variable) of which one may be suitably damped, as indicated. The inductors serve to introduce some signal peaking at the high frequency at which the circuit is operating, it being borne in mind that, as disclosed, the assumed operating frequency of the reference and variable phases is approximately 5.4- rnc. and some signal degeneration has inherently occurred in the cathode follower connected tubes 135 and 146.

The output from the tube 157 representing the added signals as amplified is then fed into a peak detector circuit, conventionally represented at 114. These signals are supplied by way of the condenser 164 to the diode 165, the opposite terminal of which connects to a point on the potentiometer use which will serve to set the level at which the Schmitt trigger 113, later to be described, can operate. The signal is also passed through a second diode element 167 and thence via the grid resistor 168 to the grid or control electrode 169 of the first half of a tube 17% which tube half constitutes a part of the so-called Schmitt trigger.

The Schmitt trigger operates in well-known fashion and consists of a double envelope-type having its plate or anode electrodes supplied with a positive potential from a suitable source (not shown), connected to the terminal point 171 and thence to the separate plates or anodes 173 and 175' by way of the plate resistors 176 and 177. As is well known, the cathode elements of the Schmitt trig ger are connected together, as shown, and connect through a cathode resistor 179 to ground at point 137. The trigger operates in such a fashion that the triggering level is set by the tapping point on the potentiometer 166 which tapping point, in the magnitude of the voltage available, has been indicated by the dotted line on the curve adjacent to the conductor 116 of FIG. 4. The general waveform is also indicated by the wave adjacent to the input resistor 168 so that when a positive pulse is arriving on the grid 169 of the tube 171) current is caused to flow through the first half ofthe tube which immediately blocks the second half in a fashion well known. This effect produces a pulse at the output which is available across the voltage divider combination including the resistors 183 and 185 at the tapping point 186. The right hand half of the tube 170 is held inoperative during the entire period of operation of the left half of the tube as occasioned by the input signal voltage exceeding the threshold bias applied. As soon as the signal input to the grid 159 is less than that of the triggering level, the left half of the tube 17% cuts oif and, with cutoff there occurring, the potential effective at the grid or control electrode of the right hand half of the tube immediately rises in a positive sense and maximum current at once flows through the right hand tube half. This occurring, the left half of the tube is cut off and the voltage output is substantially of that waveform shown adjacent to the output terminal point 187, and, at lesser amplitude, appears at the junction of resistors 133 and 185.

The voltage there developed is then applied by way of conductors 189 to each of the and gate tubes 122 and 192, forming the gates 122 and 123, to provide an enabling or continuing pulse thereon.

The reference phase voltage of conductor 77 is also applied by way of conductor 1%, which may be a coaxial cable, if desired, to the grid or control electrode of tube 191 whose output is derived across the cathode resistors 193 and 193 by way of the integrating circuit formed from the resistor 1M and the condenser 195. Plate voltage for the tube 190 is applied from a terminal point 197 through an inductor 198 (if desired) and the resistor 199. Since the amplitude of the integrated signal voltage at the output of the integrating circuit 194, 195 may have dropped to a limited extent, this signal voltage is supplied through the resistor 201 and the coupling condenser 262 to the grid or control electrode of the tube 203. Tube 203, like tube 157, already described, is preferably a pentode and illustratively may be of the 6AH6 type. Operating or plate voltage is supplied from the terminal point 197 through the plate resistors 205 and 2% and the peaking inductor 207. Cathode bias is applied through cathode resistors 208 and 209 of which at least one is appropriately biased by the condenser 211i. Signal outputs from the tube 192 representing the signal of the reference phase, shifted in polarity by tube 203 are then supplied to the adding circuit, conventionally represented at 193, by coupling the output from the tube 203 through the coupling condenser 213 to the grid or input electrode of tube 214, provided with the usual grid lack resistor 215.

Tube 214 is supplied in the indicated fashion with operating voltages from the terminal 197. Its output is derived across the cathode resistors 215 and 216, serially connected, where the output is obtained at a suitable tapping point to bring the signal level commensurate with that of the variable phase signal provided on the conductor 79 which is supplied to the second tube 219 of the adder combination, as will be explained. When signal voltages are applied at the terminal 79 and through the indicated conductor to the tube 219 the output signal voltage is available at the conductor 220 and coupling capacitor where the polarity corresponds :to that of the voltage supplied to the tube grid. The tube cathode is provided with the usual cathode resistors 221 and 221 and the output signal voltage (derived in cathode-follower fashion, as above stated) is supplied as an output voltage of controlled amplitude determined by the setting position of the tapping point 22% on the cathode resistor 221. So arranged, the cathode outputs of tubes 214- and 219 are then added across resistor 225 and applied through conductor 239 to an output circuit through a suitable peaking circuit in the output of the tube 225. The input voltage is applied to the control grid of the tube 235 to which the input conductor 231) is connected. The tube 235 is supplied with operating plate voltage from the terminal point 197 through the inductor 1%, the plate resistors 236 and 237, as well as the peaking inductors. 238 and 239. Voltage is applied .to the screen electrode in the indicated fashion from terminal 197. Accordingly, tube 235 compensates for any signal amplitude loss resulting from the cathode follower connections of the preceding tubes of the circuit and the high frequencies are maintained.

Output voltage from tube 235 is then supplied to the peak detector combination comprising diodes 239 and 240, bypassed by a suitable resistor 24-1 and having the potentiometer 242 provided with an adjustable tapping point to set the triggering level. With signal output being derived across the peak detector circuit, the resulting signal voltage is applied to the control grid of a Schmitt trigger tube 260 and controls the trigger in a fashion which essentially duplicates that already described in connection with the tube and need not be here repeated. Suffice it to say that the Schmitt trigger tube 260 provides at its output square wave voltage pulses of the character indicated by FIG. 4, which pulses are then supplied across the output resistor 261 and are effective upon the grid of the tube 270. The tube 270 also derives its operating potential from the terminal point 17 and has its output made available across its cathode resistor 271.

In the illustrated instance, the tube provides an output signal voltage through the condenser 272 and conductor 273 across resistor 27 to the control grid of the gate tube 192. The output of the tube 27%} at point 275 is actually in the form of a pulse and the combination of the small condenser 272 and the resistor 274 form a differentiating circuit to apply the controlling pulses through resistor 276 to the control electrode. It has already been stated that the enabling or conditioning pulses are applied to this tube 192 by way of conductor 189 which are supplied to the suppressor grid for enabling or conditioning the gate so that, during time periods when the gate is conditioned by a positive pulse, the tube is carried to a con ducting state during the positive pulse portions of the differentiated wave appearing at the junction of the condenser 272 and the resistor 274. At these times an output signal voltage is derived across the load resistor 280 and becomes available through conductor 281 and at the terminal point 232 so that there is there provided an output signal pulse of a subtract variety indicating that the phase angle between the reference frequency and the variable frequency is decreasing.

Also available from the output of the cathode follower connected tube 27% there is a second output signal which is supplied through the coupling condenser 233 and across resistor 234 forming a differentiating combination, and then through the diode 285 to the grid or control electrode of the tube 286, the signal being applied across the grid resistor 287 which has its lower end terminal at ground potential. The cathode bias of the tube 286 is provided by way of the bypassed cathode resistor 288 to set and determine the level of the signals supplied on the input or control electrode of the tube 286. Positive potential available at an input terminal 290, through an inductor 291 and conductor 292 establishes a positive bias through the resistor 293 which biases the diode 285 above ground potential to a selected value. Consequently, although the signal amplitude available at the input or control electrode of the tube 27% may be as much as 30 volts, for instance, the applied bias may be set at such value that the signal magnitude available at the input grid or control electrode of the tube 286 is reduced to the order of a few volts.

It will be recalled from the diagrammatic showing of FIG. 4 that whatever control pulses are provided upon the and gate 122 are inverted in phase with respect to those pulses applied to the and gate 123, hence the inversion is provided in the tube 286 which amplifies the signal level and provides the amplified signal across the plate resistor 297 and the coupling condenser 298 to the control electrode or grid of the tube 193. The bias on the tube is set by way of the grid resistor 299, tapped to a point of selected value on the voltage divider comprising resistors 301 and 3tl2. Consequently, at times when the gate tube 193 is supplied with an enabling or conditioning pulse in the positive direction by way of conductor 189, it can be seen that an input pulse supplied at the time a positive voltage is effective on the suppressor grid produces output pulses available across the plate resistor 305 and conductor 83 to terminal 233.

Now making reference to FIG. 5, a zero crossing coincidence detector provided for a Vernier reset is described generally in connection with the schematically indicated component 89 in FIG. 3. By FIG. 5 the pulse input voltage is available upon the conductors 9t and 91 and is of a waveform there generally depicted. These pulses are applied to the transistor circuits. Considering the input pulse on the conductor 90, this voltage pulse is applied to the base electrode of the transistor 315, to the emitter of which a positive biasing voltage of the order of 10 volts relative to ground potential may be applied from a suitable source (not shown), connected at the terminal point 316 and connected to the emitter through the resistor 317. The input voltage is applied through a pair of resistors 318 and 319 and across resistor 32% connected with one terminal to the junction of resistors 318 and 319 and with the other terminal connected to ground 137. Since the pulse applied along the conductor 90 is often of substantial value, the diode 322 serves to limit the voltage that can be applied to the base and thus protects the transistor element.

The voltage applied by way of conductor 90, being in the form of pulses, causes current instantaneously to flow through the transistor and the resistor 323 and coil 324 to ground. Coil 324 is bypassed by a diode 325 in wellknown fashion to damp any oscillations across the coil. The diode 325 may be of any suitable and known type but it has been found that a transistor, such as that shown at 315, is one where a component of the 2N247 type is highly satisfactory. With the cutting off the pulse activation of the transistor 315 the coil 324 having the indicated shunt distributed capacity, breaks into oscillation with the inductor 324 and the distributed capacity providing a ringing circuit. The ringing effect is highly damped by the diode 325 (usually of the 1N67A type). The first positive pulse of the produced oscillation is applied through the diode 327 (also of the same type) to be added to the output of a second transistor element 336, later to be described, and made available as an input or control signal across the resistor 331 and through resistor 332. The effective output is a pulse of the first negative half cycle and of about a 0.2 microsecond duration. The positive half cycle is prevented from reaching the output by the diode 325.

Pulse voltage of the waveform available on the conductor 91 is applied to the transistor element 330 (again an element preferably of the 2N247 type) in a fashion similar to that already explained relative to the transistor 315, it being understood, of course, that the waveform on the conductor 90 will be assumed to represent the controlled reference oscillator and that available on the conductor 91 will represent the variable oscillator. Since the two portions of the circuit function in identical fashion, like parts are similar and are numbered with primed numbers and will not be discussed further.

It is safe to say that the output signals from transistor 33% combine with those of transistor 315 and add across resistor 331 to feed the and gate provided by transistor 341. Resistor 332 is normally adjusted for twice the maximum triggering voltage so that, when there is phase coincidence between the output pulses available on conductors 9d and 91, this pulse voltage will be supplied to the base of transistor 341 through the condenser 342. It will be seen that the transistor 341 (which is preferably one of the 6T761 type) is connected with the transistor 315 as an emitter follower. Such voltage as is available through the emitter-coupled transistor 341 is then supplied through the coupling condenser 345 to the transistors 346 and 347 (also preferably of the 6T761 type) connected as a delay inultivibrator. The cross-connection between the multivibrator and the two parts thereof is provided by the parallel combination provided by the resistor 343 and the condenser 349. The transistors 346 and 347, working together, function essentially as a oneshot multivibrator whose period is controlled by the time constant established for the circuit by the appropriate choice of the condenser 349 and the resistor elements 350 and 359'. The signal pulse output from the transistor delay multivibrator is then amplified and broadened out by the transistor 355 (usually a 2N192 type), the output of which is obtained across the resistor 357 and made available at the terminal 369, from there to be applied, illustratively, to control some suitable form of control device which may be of any desired character, such as a blocking oscillator, to reset the counter mechanism in accordance with the conditions instantaneously obtaining.

Where a blocking oscillator (not shown) is used as a reset circuit it usually functions in combination with a suitable up-down circuit which need not here be described. The control is generally well known as a form of control for an indicator tube of the add or subtract type, such as the Burroughs-tube type BBL-301. The operation is such that all electrodes of the tube are carried to a state that the beam developed within the tube is blanked and then finally, following a short time interval on the reset phase, the tube is again driven to an operating state with the indication produced at a zero marker thereon. I At that point it may be restated that the up-down counter chassis preferably comprises three decade up-down counters. This chassis usually also includes certain plug-in printed circuit boards which contain diode matrices as well as the drive circuit for degree acquisition of the code plate system which has been generally referred to herein and which, it will be recalled, serves to control the continuous output of the degree counter 86, but which is generally auxiliary to the instant invention. In the up-down counter, it will be understood, that this has been shown merely diagrammatically since various forms of up-down counters are known and used in the art. Among the groups making and providing up-down counters which are suitable for use in connection with the present apparatus and which are suitable for controlling the operation of the already-described Burroughs-type BID-301 registering tube, are counters made by the Victor Adding Machine Company of Chicago and counters made by Di/An Instrument Company of Boston, Mass. Essentially the indicator tubes of the suggested types are connected in a complernentary fashion so that the so-called subtract pulses function to produce indications on one of the tubes, and the so-called add pulses produce indications on the other tu e. Other forms of the up-down counters and indicat dr components (tubes or other forms) well known to those skilled in the art may also be used and the schematic drawing herein is thus considered illustrative and not limiting. Suihce it, tierefore, to say that the counter mechanism is controlled as schematically indicated and is used in connection with the other circuit components herein either specifically or diagrammatically set forth.

It has already been explained that regardless of the precision which is mechanically built into the transducer element, certain changes occur to produce slowly fluctuating amplitudes of the hi h frequency signal voltages developed in the generation of the signal voltages by the rotor and stator elements. Many explanations can be given for these changes but it has been found that almost without exception the variances in amplitude cannot be mechanically compensated. The result is that there is a phase and amplitude imperfection that must be compensated and the circuitry of FIG. 7 provides for achieving this result. In the form of circuit shown by FIG. 7 voltage of one of the two developed reference or adjustable frequencies is sup lied at the input terminal 491 and from there to the grid or control electrode 462 of a tube 4&3. The tube 433 has its plate or anode voltage supplied from a source (not shown) connected to the terminal point 435, the source being poled positively relative to the tube plate. The tube cathode 4% connects to ground 137 through the cathode resistor 4%.

An output voltage in phase with the input and fluctuating in amplitude in the same fashion as the input is obtained from the cathode follower and supplied through the coupling condenser 4-559 to the peak detector circuit which comprises the diodes 416) and 411 with the resistor 412 connected across diode 41%. This provides peak detection of the input amplitude fluctuations and the amplitude varying signals are supplied through the integrating circuit provided by the capacitors M3 and 414 between which is the resistor 415 to be supplied for amplification to the input or control electrode 417 of the tube did. There is thus provided, as the input voltage, fluctuations occurring at the rate of change of the input signal amplitude.

The electronic system here described is generally of limited sensitivity to amplitude but extremely sensitive to phase changes. The jitter circuit above described makes use of the fact that amplitude fluctuations are present through the amplitude detection of the envelope of the transducer output, which is put through a phase shifting and gain control circuit.

In the diagramrned circuit tube 418 is supplied with plate voltage from terminal W5 through plate resistor 4T9. Cathode bias is derived through cathode resistor 419'. Output voltage from the tube is available at both the tube plate and cathode or across resistors 419 and 419. The voltages are then supplied to the conductors of a doublepole, double-throw switch 426 to be made available in an output conductor 425 either through capacitor 421 or resistor 4-22 and through resistors 423 and 424 to the latter of which the output coaxial conductor is adjustably connected.

As can be seen clearly from FIG. 3, the output available on the conductor 425 is then applied as a control voltage to control the amplitude of the oscillator 57. The control is applied as a modulation of the oscillator in wellknown fashion and need not be explained in further detail.

Similar jitter compensation is provided for both the reference and variable channels and therefore a single unit is diagrammed but separate units are used in each channel as clearly shown by FIG. 3.

In the foregoing apparatus many and various tube types as well as transistor types may be used. In some instances in the description of the invention tube types were mentioned. In other instances in the description reference was made to particular transistor types. For purposes of designating various forms of tubes in the circuits in many cases the tube types are shown with tube envelopes which are not closed. This is because of the fact that the operating tube in question may comprise only half or a portion of a particular tube. The adjacent tube frequently constitutes the other half tube, but this is not necessarily the case and, consequently, for clarity of showing, the designated form is preferred.

For reference to particular tube types (and here the tube type will be named without regard to whether the complete tube is used at the point or whether only a portion of the tube is used) the following schedule may be noted.

Part No.: Tube No.

In the description which precedes reference 5 made in each instance to the preferred form of transistor component, it will be recognized that each of the transistors and tubes may be replaced by another component of generally equal efficiency without impairing the circuit operation. No schedules of values of resistors, indicators, or condensers have been given since these may be varied quite widely. Experiment and general familiarity with circuits and their application will readily establish the size component to use considering the apparatus as disclosed and in accordance with the particular frequency values selected together with the time base of operation provided.

Many and varied modifications may be made to the cir cuitry here claimed and described. Therefore, it is believed that the claims hereinafter appended should be considered broadly and limited only insofar as prior art limitations necessitate it.

Having now described the invention what is claimed is:

1. Apparatus for providing encoded information indicative of the relative relationship of two electrical conditions with respect to each other which comprises means for generating a first signal indication repeating at a preselected frequnecy rate, means to generate a second signal indication of a frequnecy substantially corresponding to that of the first signal indication and subject to change phase with respect thereto, means for generating separate electrical signal waves each of a harmonic of each fundamental frequency generated and therefrom producing a signal indicative of the departure in phase between the second and first generated signals and means for converting the produced signal into a digital indication of the departure in either advanced or retarded phase relationship between the second and first developed signals.

2. Apparatus for providing encoded information indicative of the relative relationship of two electrical conditions with respect to each other which comprises means for generating two separate signal indications each repeating at a preselected frequency rate, means to introduce a phase shift in one of the signals relative to the other, means for generating harmonically related signals of each of the two separate signal indications, means for com paring the two harmonically related signals after phase shift for producing a signal indicative of the departure in phase between the two developed signals and means for converting the produced signal into a digital indication of the extent of departure in either advanced or retarded phase relationship between the developed signals.

3. Apparatus for registering the relationship of two electrical quantities each indicative of a preselected quantity which comprises means to generate a pair of electrical signals each of substantially like frequency value of which the phase relationship of one is subject to be advanced or retarded with respect to the other by an unknown quantity, a pair of oscillation generators each generating an electrical signal wave at a frequency which is a harmonic of each fundamental frequency generated, means to introduce a phase departure in one of the electrical signals of the first pair with the phase departure being in the direction of advancing phase or retarded phase in accordance with an electrical quantity to be determined, means for providing an indication in the harmonic signal waves of the direction of phase departure of the variable one of the pair of generated frequencies relative to the other and means for registering the said departure.

4. Apparatus for registering the relationship of two electrical quantities each indicative of a preselected quantity which comprises means to generate a pair of electrical signals each of substantially like frequency value of which the phase relationship of one signal is subject to be advanced or retarded with respect to the other by an unknown quantity, a pair of oscillation generators each for generating a frequency which is a harmonic of each fundamental frequency generated, means for stabilizing the developed harmonic frequencies under the control of the generated electrical signals and thereby establishing an interlock between the fixed reference and variable values of the first generated signals and the harmonic frequencies generated by the oscillation generator, means to introduce a phase departure in one of the electrical signals of the first pair relative to the other signal with the phase departure being in the direction of advancing phase or retarded phase in accordance with an electrical quantity to be determined, means for producing a proportional change in the generated waves of harmonically related frequency, means under the control of the generated waves of harmonically related frequency for registering both the direction and extent of phase departure of the variable one of the pair of generated frequencies with respect to the reference one.

5. Apparatus for registering the relationship of two electrical quantities each indicative of a preselected quantity which comprises means to generate a pair of electrical signals each of substantially like frequency value, means to advance or retard the phase relationship of one signal with respect to the other by an electrical quantity to be determined, a pair of oscillation generators each generating a frequency which is a harmonic of each fundamental frequency generated, means for stabilizing each developed harmonic frequency by the generated electrical signals and thereby establishing an interlock between the first generated signals and the harmonic frequencies generated by the oscillation generator, means for providing signal indications of the direction and extent of phase departure of the variable one of the pair of generated harmonically related frequencies and means for registering the said indications.

6. An electromechanical transducer for converting angular changes in the electrical relationship between two generated electrical waves, comprising a plurality of signal generators each adapted to be driven at a selected rate to develop electrical waves normally of like frequency, means to change the phase of one of the generated signals relative to the other in proportion to a signal phenomena to be measured, means to develop a pair of electrical waves each having an harmonic relationship to the frequency normally developed by each of the plurality of signal generating means, means to divide each harmonic frequency to transform it to a frequency substantially corresponding to that of each of the plurality of signal generators, means to phase-compare the first pair of generated signals and the divided harmonic frequencies of the second generated signals to produce control signals, means stabilized by the control signals to lock the multiple frequency to the initially generated frequency in a phase relationship corresponding to that of the first generated electrical waves, and means for registering the relative phase departure of the harmonically related frequencies to produce visible indications of advancing and retarding phase relationships.

7. An electromechanical transducer for converting angular positions into encoded digital values which comprises the combination of a pair of signal generators each having a common rotor and separate stators, a drive means for simultaneously rotating the rotor elements relative to the separate stators, means to change the angular position of one of the stator elements relative to the rotors while holding the other stator element fixed to change the phase relationship between the generated signals derived from the adjusted stator-rotor combination with respect to the other signal as a reference value thereby to provide a changing phase relationship between the two developed signals with incremental changes being proportional to changes in relative angular position changes between the adjustable elements of each generating means, means to develop an harmonic frequency of each produced wave, means to phase each harmonic frequency to one of the generated fundamental frequencies, and means for converting differences in phase angle relationship between the generated harmonically related fre quencies into visually observable quantities with the number of separate indicati'ons per degree of mechanical shift between the stator and rotor being proportional to the harmonic relationship between the generated harmonic frequency and the originally developed frequency.

8. The transducer claimed in claim 7 wherein the conversion of the waves of harmonically related frequencies to visually observable qualities comprises means to compare the phase relationship of each generated harmonic frequency to develop signals indicative of the direction and extent of phase change relative to the reference frequency.

9. The transducer claimed in claim 7 wherein the conversion of the waves of harmonically related frequencies to visually observable qualities comprises means to register indicia of the phase discrepancy between the two signals and means to reset the registering means to a zero reading state at such time of phase coincidence.

10. Apparatus for registering the relationship of two electrical quantities each indicative of a preselected quantity which comprises transducer means to generate a pair of electrical signals each of substantially like frequency value, means for changing the phase relationship of one of the signals by advancing or retarding it with respect to the other signal as a reference by an unknown quantity, a pair of oscillation generators each generating a frequency which is a harmonic of each fundamental frequency generated, a frequency divider connected to receive each harmonic frequency and to develop therefrom an output frequency corresponding to the two generated frequencies from the transducer, phase detector means for stabilizing one developed harmonic frequency by the generated electrical signals of reference phase and the other harmonic frequency by the generated signals of variable phase thereby to establish an interlock between the first generated signals and the harmonic frequencies, means to compare the phase relationship of the generated harmonic frequencies and to produce signals indicative of the direction of phase change, and means for producing an electrical signal pulse series indicating the phase change from coincidence and means for displaying an indication of the direction of phase departure of the variable one of the pair of generated frequencies.

11. The circuit claimed in claim 4 comprising, in addition, a jitter compensating circuit connected to receive the transducer-generated voltage at its input, said jitter compensating circuit comprising a peak detector for detecting amplitude variations in the transducer-generated voltage, a phase shifting circuit connected to receive the rectified amplitude output of the voltage generated by said transducer, and means to modulate the phase of the generated multiple frequency under the control of the rectified signals indicative of amplitude change of the transducergenerated signal voltage.

(References on following page) 2 References Cited in the file of this patent UNITED STATES PATENTS Kenyon Oct. 9, 1951 20 5 Darlington Jan. 29, 1957 Speller Feb. 10, 1959 McVey June 30, 1959 Kronacher July 7, 1959 Lesti July 28, 1959 Poole Aug. 25, 1959 Bower Aug. 2, 1960 

10. APPARATUS FOR REGISTERING THE RELATIONSHIP OF TWO ELECTRICAL QUANTITIES EACH INDICATIVE OF A PRESELECTED QUANTITY WHICH COMPRISES TRANSDUCER MEANS TO GENERATE A PAIR OF ELECTRICAL SIGNALS EACH OF SUBSTANTIALLY LIKE FREQUENCY VALUE, MEANS FOR CHANGING THE PHASE RELATIONSHIP OF ONE OF THE SIGNALS BY ADVANCING OR RETARDING IT WITH RESPECT TO THE OTHER SIGNAL AS A REFERENCE BY AN UNKNOWN QUANTITY, A PAIR OF OSCILLATION GENERATORS EACH GENERATING A FREQUENCY WHICH IS A HARMONIC OF EACH FUNDAMENTAL FREQUENCY GENERATED, A FREQUENCY DIVIDER CONNECTED TO RECEIVE EACH HARMONIC FREQUENCY AND TO DEVELOP THEREFROM AN OUTPUT FREQUENCY CORRESPONDING TO THE TWO GENERATED FREQUENCIES FROM THE TRANSDUCER, PHASE DETECTOR MEANS FOR STABILIZING ONE DEVELOPED HARMONIC FREQUENCY BY THE GENERATED ELECTRICAL SIGNALS OF REFERENCE PHASE AND THE OTHER HARMONIC FREQUENCY BY THE GENERATED SIGNALS OF VARIABLE PHASE THEREBY TO ESTABLISH AN INTERLOCK BETWEEN THE FIRST GENERATED SIGNALS AND THE HARMONIC FREQUENCIES, MEANS TO COMPARE THE PHASE RELATIONSHIP OF THE GENERATED HARMONIC FREQUENCIES AND TO PRODUCE SIGNALS INDICATIVE OF THE DIRECTION OF PHASE CHANGE, AND MEANS FOR PRODUCING AN ELECTRICAL SIGNAL PULSE SERIES INDICATING THE PHASE CHANGE FROM COINCIDENCE AND MEANS FOR DISPLAYING AN INDICATION OF THE DIRECTION OF PHASE DEPARTURE OF THE VARIABLE ONE OF THE PAIR OF GENERATED FREQUENCIES. 